1. Field of the Invention
This invention relates to a pheromonally based composition and methods for its use in the control of the pecan weevil, Curculio caryae (Horn).
2. Description of the Prior Art
The pecan weevil, Curculio caryae (Horn) is a serious economic pest of pecans (Caryae illinoensis Koch), attacking maturing fruit in late summer and causing damage thereto through the making of feeding and oviposition punctures. The larvae, upon completing development in the nut, leave through a small hole in the shell and burrow into the soil. The weevils remain there for a period of 2-3 years before emerging as adults to commence another cycle.
Van Cleave and Harp in an article entitled "The Pecan Weevil: Present Status and Future Prospectives" (Proc. 64th Ann. Conv. Southeast Pecan Growers Assoc. pp. 99-111, 1971), reported that field-caged female pecan weevils attracted more weevils of both sexes than did caged male weevils. Polles et al. in an article entitled "Attraction of the Pecan Weevil to its Natural Pheromone and Grandlure" (Pecan South 4:26-28, 1977), reported on field studies in which wing-type traps, each baited with 6 live females and pecan nutlets for food, captured 85 pecan weevils (73% males). The same number of traps, baited with males captured 56 weevils (66% males), and blank traps captured 55 weevils (65% males). Polles et al., also baited traps with one or more of the components of the pheromone of the boll weevil Anthonomus grandis grandis Boheman (Tumlinson et al., "Identification and Synthesis of the Four Compounds Comprising the Boll Weevil Sex Attractant" J. Org. Chem. 36:2616-2621, 1971), on the premise that related insects may biosynthesize and respond to related compounds. A total of 23 pecan weevils (87% male), were captured with the 4-component mixture, grandlure. With (+)-cis-2-isopropenyl-1-methylcyclobutaneethanol (Component I alone), the captures totaled 7 (86% males); with (Z)-3,3-dimethyl-.DELTA..sup.1,.beta. -cyclohexaneethanol (II), there were 15 (100% males); and with (Z) and (E)-3,3-dimethyl-.DELTA..sup.1, -cyclohexaneacetaldehyde (III and IV), there were 10 (90% males). However, the blank captured about as many as did individual components: 10 weevils (70% males). Therefore, none of these tests were sufficiently comprehensive to permit statistical evaluations and in no instance was further work reported.
Mody et al., in an article entitled "Pecan Weevil Sex Attractant: Bioassay and Chemical Studies" (J. Insect. Physiol. 19:2063-2071, 1973), bioassayed fractions obtained from volatile oils of each sex of pecan weevils in field tests. Primarily males were trapped with female fractions, and primarily females were trapped with male factions. GLC-MS was used to identify a number of volatile components from the male and female oils, but on the basis of their structures, none appeared capable of accounting for the attractancy of either sex.
Hedin et al., "Sex Pheromones of the Male and Female Pecan Weevil, Curculio caryae: Behavioral and Chemical Studies" (Environ. Entomol. 8:521-523, 1979), showed that male and female pecan weevils were attractive to their opposite sex using a newly developed laboratory bioassay. Extracts of males attracted females and vice versa. (Z)-3,3-dimethyl-.DELTA..sup.1,.beta. -cyclohexaneethanol was identified as present in a weevil extract and shown to possess some attractiveness to both sexes in preliminary field bioassays, used either as adsorbents or catalysts.
While various methodologies and pheremonal compositions exist for the control of other insect species, there remains a need for the creation of such tools for use with the pecan weevil.